Technique to reduce the zeolite molecular sieve solubility in an aqueous system

ABSTRACT

This invention relates to an improved adsorbent comprising a crystalline aluminosilicate, method of manufacture of the adsorbent and improved process for separating a component from a feed mixture comprising an aqueous solution of a mixture of different components, such as a mixture of saccharides. In the process the mixture is contacted with the adsorbent, which selectively adsorbs a component from the feed mixture. The adsorbed component is then recovered by contacting the adsorbent with a desorbent material such as water to effect the desorption of the adsorbed component from the adsorbent. There is an undesirable tendency for the silicon constituent of the crystalline aluminosilicate to dissolve in the aqueous system. The improvement to the adsorbent and process comprises the incorporation of a binder material in the adsorbent comprising a cellulose ether which substantially reduces the undesirable dissolution. The adsorbent is manufactured by mixing together powder of the crystalline aluminosilicate, powders of the binder, and a liquid organic solvent, extruding the mixture into an extrudate and drying the extrudate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of art to which this invention pertains is solid-bedadsorptive separation. More specifically, the invention relates to animproved adsorbent, method of manufacture of the adsorbent and improvedprocess for separating a component from a mixture comprising an aqueoussolution of a mixture of different components which process employs anadsorbent comprising a crystalline aluminosilicate which selectivelyadsorbs a component from the feed mixture.

2. Prior Art

It is known in the separation art that certain crystallinealuminosilicates referred to as zeolites can be used in the separationof a component from an aqueous solution of a mixture of differentcomponents. For example, adsorbents comprising crystallinealuminosilicate are used in the method described in U.S. Pat. No.4,014,711 to separate fructose from a mixture of sugars in aqueoussolution including fructose and glucose.

It is also known that crystalline aluminosilicates or zeolites are usedin adsorption processing in the form of agglomerates having highphysical strength and attrition resistance. Methods for forming thecrystalline powders into such agglomerates include the addition of aninorganic binder, generally a clay comprising silicon dioxide andaluminum oxide to the high purity zeolite powder in wet mixture. Theblended clay zeolite mixture is extruded into cylindrical type pelletsor formed into beads which are subsequently calcined in order to convertthe clay to an amorphous binder of considerable mechanical strength. Asbinders, clays of the kaolin type are generally used.

Zeolite crystal and inorganic binder agglomerates have long been knownto have the property of gradually disintegrating as a result ofcontinuous contact with water. This disintegration has been observed asa silicon presence or contamination in the solution in contact with theadsorbent. Such contamination may at times be sufficiently severe toimpart a cloudy appearance to the solution.

It is further known that certain water permeable organic polymers,particularly cellulose ester and cellulose nitrate, are advantageouslyused as adsorbent binders in that they reduce the extent of dissolutionof the silicon constituent and the extent of disintegration of theadsorbent when used in an aqueous system.

We have discovered an improved adsorbent, a method of manufacturing theadsorbent and an improvement to an aqueous separation process whichfurther minimizes the disintegration of the adsorbent siliconcontamination of the product.

SUMMARY OF THE INVENTION

Accordingly, the objectives of our invention are (1) to provide animprovement to a process for the separation of a component from a feedmixture comprising different components in aqueous solution bycontacting said mixture with an adsorbent comprising a crystallinealuminosilicate so as to minimize the dissolution of the crystallinealuminosilicate and silica contamination of the product; (2) to developan adsorbent composition suitable for use in the process of the firststated objective; and (3) to provide a method of manufacture of suchadsorbent.

In brief summary, our invention is, in one embodiment, an improvedprocess for the separation of a component from a feed mixture comprisingan aqueous solution of a mixture of components by contacting thesolution with an adsorbent comprising a crystalline aluminosilicateexhibiting an adsorptive selectivity towards the component. Thecomponent is thereby selectively adsorbed from the mixture, andthereafter recovered. The silicon constituent of the adsorbent tends todissolve in the solution resulting in the undesirable disintegration ofthe adsorbent. The improvement to the process comprises theincorporation of a binder material in the adsorbent comprising acellulose ether, which substantially reduces the extent of dissolutionof the silicon constituent and the extent of the disintegration of theadsorbent.

In another embodiment, our invention is an adsorbent comprising acrystalline aluminosilicate suitable for use in a process for theseparation of a component from a feed mixture comprising an aqueoussolution of a mixture of components by contacting the solution with theadsorbent. The silicon constituent of the adsorbent tends to dissolve inthe solution resulting in the undesirable disintegration of thecrystalline aluminosilicate. The improvement to the adsorbent comprisesthe incorporation of a binder material in the adsorbent comprising acellulose ether which incorporation substantially reduces the extent ofdissolution of the silicon constituent and the extent of thedisintegration of the adsorbent.

In still another embodiment, our invention is a method for themanufacture of an adsorbent comprising crystalline aluminosilicate and acellulose ether binder suitable for use in a process for the separationof a component from a feed mixture comprising an aqueous solution of amixture of components. The method comprises: (a) mixing together apowder of crystalline aluminosilicate, a powder of the binder and aliquid organic solvent to form a malleable mixture; (b) forming saidmalleable mixture into discrete formations; (c) removing the solventfrom the formations to obtain hard dry formations; and (d) breaking thehard dry formations into particles of desired sizes.

Other objects and embodiments of our invention encompass details aboutfeed mixtures, adsorbents, binder materials, solvents, desorbentmaterials and operating conditions, all of which are hereinafterdisclosed in the following discussions of each of the facets of thepresent invention.

DESCRIPTION OF THE INVENTION

At the outset the definitions of various terms used throughout thespecification will be useful in making clear the operation, objects andadvantages of our process.

A feed mixture is a mixture containing one or more extract componentsand one or more raffinate components to be separated by my process. Theterm "feed stream" indicates a stream of a feed mixture which passes tothe adsorbent used in the process.

An "extract component" is a component that is more selectively adsorbedby the adsorbent while a "raffinate component" is a component that isless selectively adsorbed. The term "desorbent material" shall meangenerally a material capable of desorbing an extract component. The term"desorbent stream" or "desorbent input stream" indicates the streamthrough which desorbent material passes to the adsorbent. The term"raffinate stream" or "raffinate output stream" means a stream throughwhich a raffinate component is removed from the adsorbent. Thecomposition of the raffinate stream can vary from essentially 100%desorbent material to essentially 100% raffinate components. The term"extract stream" or "extract output stream" shall mean a stream throughwhich an extract material which has been desorbed by a desorbentmaterial is removed from the adsorbent. The composition of the extractstream, likewise, can vary from essentially 100% desorbent material toessentially 100% extract components. At least a portion of the extractstream, and preferably at least a portion of the raffinate stream, fromthe separation process are passed to separation means, typicallyfractionators or evaporators, where at least a portion of desorbentmaterial is separated to produce an extract product and a raffinateproduct. The terms "extract product" and "raffinate product" meansproducts produced by the process containing, respectively, an extractcomponent and a raffinate component in higher concentrations than thosefound in the extract stream and the raffinate stream.

The term "selective pore volume" of the adsorbent is defined as thevolume of the adsorbent which selectively adsorbs an extract componentfrom the feed mixture. The term "non-selective void volume" of theadsorbent is the volume of the adsorbent which does not selectivelyretain an extract component from the feed mixture. This volume includesthe cavities of the adsorbent which contain no adsorptive sites and theinterstitial void spaces between adsorbent particles. The selective porevolume and the non-selective void volume are generally expressed involumetric quantities and are of importance in determining the properflow rates of fluid required to be passed into an operational zone forefficient operations to take place for a given quantity of adsorbent.When adsorbent "passes" into an operation zone (hereinafter defined anddescribed) employed in one embodiment of this process, its non-selectivevoid volume, together with its selective pore volume, carries fluid intothat zone. The non-selective void volume is utilized in determining theamount of fluid which should pass into the same zone in acounter-current direction to the adsorbent to displace the fluid presentin the non-selective void volume. If the fluid flow rate passing into azone is smaller than the non-selective void volume rate of adsorbentmaterial passing into that zone, there is a net entrainment of liquidinto the zone by the adsorbent. Since this net entrainment is a fluidpresent in non-selective void volume of the adsorbent, it, in mostinstances, comprises less selectively retained feed components. Theselective pore volume of an adsorbent can in certain instances adsorbportions of raffinate material from the fluid surrounding the adsorbent,since in certain instances there is competition between extract materialand raffinate material for adsorptive sites within the selective porevolume. If a large quantity of raffinate material with respect toextract material surrounds the adsorbent, raffinate material can becompetitive enough to be adsorbed by the adsorbent.

The so-called "simple sugars" are classified as monosaccharides and arethose sugars which upon hydrolysis do not break down into smallersimpler sugars. One may further classify monsaccharides as aldoses orketoses, depending upon whether they are hydroxy aldehydes or hydroxyketones, and by the number of carbon atoms in the molecule. Most commonand well known are probably the hexoses. Common ketohexoses are fructose(levulose) and sorbose; common aldohexoses are glucose (dextrose),mannose and galactose. The term "oligosaccharides", as commonlyunderstood in the art and as used herein, means simple polysaccharidescontaining a known number of constituent monosaccharide units. Anoligosaccharide that breaks up upon hydrolysis into two monosaccharideunits is called a disaccharide, examples being sucrose, maltose, andlactose. Those giving three such units are trisaccharides, of whichraffinose and melezitose are examples. Di-, tri- and tetra-saccharidescomprise practically all of the oligosaccharides. The term"polysaccharide" includes oligosaccharides but usually it refers tocarbohydrate materials of much higher molecular weight, namely, thosethat are capable of breaking up on hydrolysis into a large number ofmonosaccharide units. Typical polysaccharides are starch, glycogen,cellulose and pentosans.

Feed mixtures which can be changed to the process of our invention may,for example, be aqueous solutions of one or more aldoses and one or moreketoses, or one or more monosaccharides and one or moreoligosaccharides. The concentration of solids in the solutions may rangefrom about 0.5 wt. % to about 50 wt. % or more, but preferably will befrom about 5 to about 35 wt. %. Starch syrups such as corn syrup areexamples of feed mixtures which can be charged to our process. Suchsyrups are produced by the partial hydrolysis of starch generally in thepresence of mineral acids or enzymes. Corn syrup produced in this mannerwill typically contain 25 to 75 wt. % solids comprising 90 to 95%glucose and 5 to 10% maltose and higher oligosaccharides. A portion ofthe glucose in this corn syrup may be isomerized with an isomerizingenzyme to produce a high-fructose corn syrup, typically comprising40-45% fructose, 50-55% glucose and 5-10% oligosaccharides, which canalso be charged to our process. The pH of the aqueous solutioncomprising the feed mixture may be from about 5.0 to about 8.0.

Desorbent materials used in various prior art adsorptive separationprocesses vary depending upon such factors as the type of operationemployed. In the swing-bed system, in which the selectively adsorbedfeed component is removed from the adsorbent by a purge stream,desorbent selection is not as critical and desorbent material comprisinggaseous hydrocarbons such as methane, ethane, etc., or other types ofgases such as nitrogen or hydrogen, may be used at elevated temperaturesor reduced pressures or both to effectively purge the adsorbed feedcomponent from the adsorbent, if the adsorbed feed component isvolatile. However, in adsorptive separation processes which aregenerally operated continuously at substantially constant pressures andtemperatures to insure liquid phase, the desorbent material must bejudiciously selected to satisfy many criteria. First, the desorbentmaterial should displace an extract component from the adsorbent withreasonable mass flow rates without itself being so strongly adsorbed asto unduly prevent an extract component from displacing the desorbentmaterial in a following adsorption cycle. Expressed in terms of theselectivity (hereinafter discussed in more detail), it is preferred thatthe adsorbent be more selective for all of the extract components withrespect to a raffinate component than it is for the desorbent materialwith respect to a raffinate component. Secondly, desorbent materialsmust be compatible with the particular adsorbent and the particular feedmixture. More specifically, they must not reduce or destroy the criticalselectivity of the adsorbent for an extract component with respect to araffinate component. Additionally, desorbent materials should notchemically react with or cause a chemical reaction of either an extractcomponent or a raffinate component. Both the extract stream and theraffinate stream are typically removed from the adsorbent in admixturewith desorbent material and any chemical reaction involving a desorbentmaterial and an extract component or a raffinate component would reducethe purity of the extract product or the raffinate product or both.Since both the raffinate stream and the extract stream typically containdesorbent materials, desorbent materials should additionally besubstances which are easily separable from the feed mixture that ispassed into the process. Without a method of separating at least aportion of the desorbent material present in the extract stream and theraffinate stream, the concentration of an extract component in theextract product and the concentration of a raffinate component in theraffinate product would not be very high, nor would the desorbentmaterial be available for reuse in the process. It is contemplated thatat least a portion of the desorbent material will be separated from theextract and the raffinate streams by distillation or evaporation, butother separation methods such as reverse osmosis may also be employedalone or in combination with distillation or evaporation. If theraffinate and extract products are foodstuffs intended for humanconsumption, desorbent materials should also be non-toxic. Finally,desorbent materials should also be materials which are readily availableand therefore reasonable in cost.

It has been found that water having a pH of from about 5.0 to about 8.0satisfies these criteria and is a suitable and preferred desorbentmaterial for our process. The pH of the desorbent material is importantbecause adsorption of a component by the adsorbent, removal of araffinate stream, desorption of the component from the adsorbent andremoval of an extract stream all typically occur in the presence ofdesorbent material. If the desorbent material is too acidic or tooalkaline, chemical reactions of the components are promoted and reactionproducts are produced that can reduce the yield purity of either theextract or raffinate product, or both.

Water pH does of course vary widely depending upon the source of thewater in addition to other factors. Methods of maintaining andcontrolling a desired water pH are, however, well-known to those skilledin the art of water treating. Such methods generally comprise adding analkaline compound such as sodium hydroxide or an acid compound such ashydrochloric acid to the water in amounts as necessary to achieve andmaintain the desired pH.

The prior art has recognized that certain characteristics of adsorbentsare highly desirable, if not absolutely necessary, to the successfuloperation of a selective adsorption process. Such characteristics areequally important to this process. Among such characteristics are:adsorptive capacity for some volume of an extract component per volumeof adsorbent; the selective adsorption of an extract component withrespect to a raffinate component and the desorbent material; andsufficiently fast rates of adsorption and desorption of an extractcomponent to and from the adsorbent. Capacity of the adsorbent foradsorbing a specific volume of an extract component is, of course, anecessity; without such capacity the adsorbent is useless for adsorptiveseparation. Furthermore, the higher the adsorbent's capacity for anextract component the better is the adsorbent. Increased capacity of aparticular adsorbent makes it possible to reduce the amount of adsorbentneeded to separate an extract component of known concentration containedin a particular charge rate of feed mixture. A reduction in the amountof adsorbent required for a specific adsorptive separation reduces thecost of the separation process. It is important that the good initialcapacity of the adsorbent be maintained during actual use in theseparation process over some economically desirable life. The secondnecessary adsorbent characteristic is the ability of the adsorbent toseparate components of the feed; or, in other words, that the adsorbentpossess adsorptive selectivity (B), for one component as compared toanother component. Relative selectivity can be expressed not only forone feed component as compared to another but can also be expressedbetween any feed mixture component and the desorbent material. Theselectivity (B), as used throughout this specification is defined as theratio of the two components of the adsorbed phase over the ratio of thesame two components in the unadsorbed phase at equilibrium conditions.Relative selectivity is shown as Equation 1 below:

Equation 1 ##EQU1## where C and D are two components of the feedrepresented in volume percent and the subscripts A and U represent theadsorbed and unadsorbed phases respectively. The equilibrium conditionswere determined when the feed passing over a bed of adsorbent did notchange composition after contacting the bed of adsorbent. In otherwords, there was no net transfer of material occurring between theunadsorbed and adsorbed phases. Where selectivity of two componentsapproaches 1.0 there is no preferential adsorption of one component bythe adsorbent with respect to the other; they are both adsorbed (ornon-adsorbed) to about the same degree with respect to each other. Asthe (B) becomes less than or greater than 1.0 there is a preferentialadsorption by the adsorbent for one component with respect to the other.When comparing the selectivity by the adsorbent of one component C overcomponent D, a (B) larger than 1.0 indicates preferential adsorption ofcomponent C within the adsorbent. A (B) less than 1.0 would indicatethat component D is preferentially adsorbed leaving an unadsorbed phasericher in component C and an adsorbed phase richer in component D.Ideally, desorbent materials should have a selectivity equal to about 1or slightly less than 1 with respect to all extract components so thatall of the extract components can be desorbed as a class with reasonableflow rates of desorbent material and so that extract components candisplace desorbent material in a subsequent adsorption step. Whileseparation of an extract component from a raffinate component istheoretically possible when the selectivity of the adsorbent for theextract component with respect to the raffinate component is greaterthan 1.0, it is preferred that such selectivity be greater than 2.0.Like relative volatility, the higher the selectivity the easier theseparation is to perform. Higher selectivities permit a smaller amountof adsorbent to be used. The third important characteristic is the rateof exchange of the extract component of the feed mixture material or, inother words, the relative rate of desorption of the extract component.This characteristic relates directly to the amount of desorbent materialthat must be employed in the process to recover the extract componentfrom the adsorbent; faster rates of exchange reduce the amount ofdesorbent material needed to remove the extract component and thereforepermit a reduction in the operating cost of the process. With fasterrates of exchange, less desorbent material has to be pumped through theprocess and separated from the extract stream for reuse in the process.

Adsorbents to be used in the process of this invention will comprisespecific crystalline aluminosilicates or molecular sieves. Particularcrystalline aluminosilicates encompassed by the present inventioninclude crystalline aluminosilicate cage structures in which the aluminaand silica tetrahedra are intimately connected in an open threedimensional network to form cage-like structures with window-like poresof about 8 A free diameter. The tetrahedra are cross-linked by thesharing of oxygen atoms with spaces between the tetrahedra occupied bywater molecules prior to partial or total dehydration of this zeolite.The dehydration of the zeolite results in crystals interlaced with cellshaving molecular dimensions and thus the crystalline aluminosilicatesare often referred to as "molecular sieves", particularly when theseparation which they effect is dependent essentially upon differencesbetween the sizes of the feed molecules as, for instance, when smallernormal paraffin molecules are separated from larger isoparaffinmolecules by using a particular molecular sieve.

In hydrated form, the crystalline aluminosilicates used in the processof my invention generally encompass those zeolites represented by theFormula 1 below:

Formula 1

    M.sub.2/n O:Al.sub.2 O.sub.3 :wSiO.sub.2 :yH.sub.2 O

where "M" is a cation which balances the electrovalence of thealuminum-centered tetrahedra and which is generally referred to as anexchangeable cationic site, "n" represents the valence of the cation,"w" represents the moles of SiO₂, and "y" represents the moles of water.The generalized cation "M" may be monovalent, divalent or trivalent ormixtures thereof.

The prior art has generally recognized that adsorbents comprising X andY zeolites can be used in certain adsorptive separation processes. Thesezeolites are described and defined in U.S. Pat. Nos. 2,882,244 and3,130,007 respectively incorporated herein by reference thereto. The Xzeolite in the hydrated or partially hydrated form can be represented interms of mole oxides as shown in Formula 2 below:

Formula 2

    (0.9±0.2)M.sub.2/n O:Al.sub.2 O.sub.3 :(2.50±0.5)SiO.sub.2 :yH.sub.2 O

where "M" represents at least one cation having a valence of not morethan 3, "n" represents the valence of "M", and "y" is a value up toabout 9 depending upon the identity of "M" and the degree of hydrationof the crystal. As noted from Formula 2, the SiO₂ /Al₂ O₃ mole ratio ofX zeolite is 2.5±0.5. The cation "M" may be one or more of a number ofcations such as a hydrogen cation, an alkali metal cation, or analkaline earth cation, or other selected cations, and is generallyreferred to as an exchangeable cationic site. As the X zeolite isinitially prepared, the cation "M" is usually predominately sodium, thatis, the major cation at the exchangeable cationic sites is sodium andthe zeolite is therefore referred to as a sodium-X zeolite. Dependingupon the purity of the reactants used to make the zeolite, other cationsmentioned above may be present, however, as impurities. The Y zeolite inthe hydrated or partially hydrated form can be similarly represented interms of mole oxides as in Formula 3 below:

Formula 3

    (0.9±0.2)M.sub.2/n O:Al.sub.2 O.sub.3 :wSiO.sub.2 :yH.sub.2 O

where "M" is at least one cation having a valence not more than 3, "n"represents the valence of "M", "w" is a value greater than about 3 up toabout 6, and "y" is a value up to about 9 depending upon the identity of"M" and the degree of hydration of the crystal. The SiO₂ /Al₂ O₃ moleratio for Y zeolites can thus be from about 3 to about 6. Like the Xzeolite, the cation "M" may be one or more of a variety of cations but,as the Y zeolite is initially prepared, the cation "M" is also usuallypredominately sodium. A Y zeolite containing predominately sodiumcations at the exchangeable cationic sites is therefore referred to as asodium-Y zeolite.

Cations occupying exchangeable cationic sites in the zeolite may bereplaced with other cations by ion exchange methods well-known to thosehaving ordinary skill in the field of crystalline aluminosilicates. Suchmethods are generally performed by contacting the zeolite or anadsorbent material containing the zeolite with an aqueous solution ofthe soluble salt of the cation or cations desired to be placed upon thezeolite. After the desired degree of exchange takes place, the sievesare removed from the aqueous solution, washed, and dried to a desiredwater content. By such methods the sodium cations and any non-sodiumcations which might be occupying exchangeable sites as impurities in asodium-X or sodium-Y zeolite can be partially or essentially completelyreplaced with other cations. It is preferred that the zeolite used inthe process of this invention contain cations at exchangeable cationicsites selected from the group consisting of the alkali metals and thealkaline earth metals.

Typically, adsorbents known to the prior art used in separativeprocesses contain zeolite crystals and amorphous material. The zeolitewill typically be present in the adsorbent in amounts ranging from about75 wt. % to about 98 wt. % based on volatile free composition. Volatilefree compositions are generally determined after the adsorbent has beencalcined at 900° C. in order to drive off all volatile matter. Theremainder of the adsorbent will generally be an amorphous inorganicmaterial such as silica, or silica-alumina mixtures or compounds, suchas clays, which material is present in intimate mixture with the smallparticles of the zeolite material. This amorphous material may be anadjunct of the manufacturing process for zeolite (for example,intentionally incomplete purification of either zeolite during itsmanufacture) or it may be added to relatively pure zeolite, but ineither case its usual purpose is as a binder to aid in forming oragglomerating the hard crystalline particles of the zeolite. Normally,the adsorbent will be in the form of particles such as extrudates,aggregates, tablets, macrospheres or granules having a desired particlesize range. The typical adsorbent will have a particle size range ofabout 16-40 mesh (Standard U.S. Mesh). Examples of zeolites used inadsorbents known to the art, either as is or after cation exchange, are"Molecular Sieves 13X" and "SK-40" both of which are available from theLinde Company, Tonawanda, N.Y. The first material of course contains Xzeolite while the latter material contains Y zeolite. It is known that Xor Y zeolites possess the selectivity requirement and other necessaryrequirements previously discussed and are therefore suitable for use inseparation processes.

In contradistinction to adsorbents known to the art, the adsorbent ofthis invention has incorporated therein a binder material comprising acellulose ether. We have found cellulose ethers, particularly ethylcellulose, to be far superior to binders such as cellulose nitrateand/or cellulose esters such as cellulose acetate because the former ismore resistant to hydrolysis. The preferred concentration of thecellulose ether in the adsorbent is from about 3.0 to about 50.0 wt. %.

Like some of the above discussed adsorbents of the known art, theadsorbent of this invention is in the form of particles having aparticle size range of about 16-80 mesh (Standard U.S. Mesh). Unlike theknown art adsorbents, however, the adsorbents of this invention do notrequire calcining, and, most important, achieve substantially reduceddisintegration and silicon contamination of the product stream when usedin the process of this invention. The reduced disintegration results inminimization of the undesirable increase in pressure drop through thecolumn in which the adsorbent is packed as compared to the inevitablehigh increase associated with the adsorbents of the known art.

The adsorbent of this invention is manufactured by mixing togetherpowder of the crystalline aluminosilicate, powder of the cellulose etherbinder, and a liquid organic solvent to make the mixture malleable,forming the mixture into discrete formations, removing the solvent fromthe formations and breaking the formations into the desired sizedparticles. The forming of the malleable mixture is preferably done byextrusion. The aluminosilicate and binder powders may first be mixedtogether and the solvent added to the powder mixture, or the binderpowder may be first dissolved in the solvent and the aluminosilicatepowder added to the solution. Preferred liquid organic solvents arep-dioxane, methyl-ethyl ketone, acetone, chloroform, benzyl alcohol,acetic acid, ethyl acetate, toluene and cyclohexanone, any of which maybe mixed with formamide. The solvent is removed from the formationseither by water washing followed by drying at a temperature notexceeding about 100° C., or by just drying at that temperature. Theformations are broken into particles having a preferred size such thatthe particles will pass through a No. 16 screen and be retained on a No.80 screen. Any fines resulting from the breaking of the particles notretained on a No. 80 screen may be added to thealuminosilicate-solvent-binder mixture. The particles may be furthertreated to effect ion exchange between cations at exchangeable cationicsites on the crystalline aluminosilicate in the particles and cationspreferably selected from the group consisting of alkali metals andalkali earth metals. The preferred crystalline aluminosilicate for usein this invention is a calcium exchanged Y-zeolite.

The adsorbent may be employed in the form of a dense compact fixed bedwhich is alternatively contacted with the feed mixture and desorbentmaterials. In the simplest embodiment of the invention, the adsorbent isemployed in the form of a single static bed in which case the process isonly semi-continuous. In another embodiment, a set of two or more staticbeds may be employed in fixed bed contacting with appropriate valving sothat the feed mixture is passed through one or more adsorbent beds whilethe desorbent materials can be passed through one or more of the otherbeds in the set. The flow of feed mixture and desorbent materials may beeither up or down through the desorbent. Any of the conventionalapparatus employed in static bed fluid-solid contacting may be used.

Countercurrent moving bed or simulated moving bed countercurrent flowsystems, however, have a much greater separation efficiency than fixedadsorbent bed systems and are therefore preferred for use in thisseparation process. In the moving bed or simulated moving bed processesthe adsorption and desorption operations are continuously taking placewhich allows both continuous production of an extract and a raffinatestream and the continual use of feed and desorbent streams. Onepreferred embodiment of this process utilizes what is known in the artas the simulated moving bed countercurrent flow system. The operatingprinciples and sequence of such a flow system are described in U.S. Pat.No. 2,985,589 incorporated herein by reference thereto. In such asystem, it is the progressive movement of multiple liquid access pointsdown an adsorbent chamber that simulates the upward movement ofadsorbent contained in the chamber. Only four of the access lines areactive at any one time; the feed input stream, desorbent inlet stream,raffinate outlet stream, and extract outlet stream access lines.Coincident with this simulated upward movement of the solid adsorbent isthe movement of the liquid occupying the void volume of the packed bedof adsorbent. So that countercurrent contact is maintained, a liquidflow down the adsorbent chamber may be provided by a pump. As an activeliquid access point moves through a cycle, that is, from the top of thechamber to the bottom, the chamber circulation pump moves throughdifferent zones which require different flow rates. A programmed flowcontroller may be provided to set and regulate these flow rates.

The active liquid access points effectively divide the adsorbent chamberinto separate zones, each of which has a different function. In thisembodiment of this process, it is generally necessary that threeseparate operational zones be present in order for the process to takeplace although in some instances an optional fourth zone may be used.

The adsorption zone, zone 1, is defined as the adsorbent located betweenthe feed inlet stream and the raffinate outlet stream. In this zone, thefeedstock contacts the adsorbent, an extract component is adsorbed, anda raffinate stream is withdrawn. Since the general flow through zone 1is from the feed stream which passes into the zone to the raffinatestream which passes out of the zone, the flow in this zone is consideredto be a downstream direction when proceeding from the feed inlet to theraffinate outlet streams.

Immediately upstream with respect to fluid flow in zone 1 is thepurification zone, zone 2. The purification zone is defined as theadsorbent between the extract outlet stream and the feed inlet stream.The basic operations taking place in zone 2 are the displacement fromthe non-selective void volume of the adsorbent of any raffinate materialcarried into zone 2 by the shifting of adsorbent into this zone and thedesorption of any raffinate material adsorbed within the selective porevolume of the adsorbent or adsorbed on the surfaces of the adsorbentparticles. Purification is achieved by passing a portion of extractstream material leaving zone 3 into zone 2 at zone 2's upstreamboundary, the extract outlet stream, to effect the displacement ofraffinate material. The flow of material in zone 2 is in a downstreamdirection from the extract outlet stream to the feed inlet stream.

Immediately upstream of zone 2 with respect to the fluid flowing in zone2 is the desorption zone or zone 3. The desorption zone is defined asthe adsorbent between the desorbent inlet and the extract outlet stream.The function of the desorption zone is to allow a desorbent materialwhich passes into this zone to displace the extract component which wasadsorbed upon the adsorbent during a previous contact with feed in zone1 in a prior cycle of operation. The flow of fluid in zone 3 isessentially in the same direction as that of zones 1 and 2.

In some instances, an optional buffer zone, zone 4, may be utilized.This zone, defined as the adsorbent between the raffinate outlet streamand the desorbent inlet stream, if used, is located immediately upstreamwith respect to the fluid flow to zone 3. Zone 4 would be utilized toconserve the amount of desorbent utilized in the desorption step since aportion of the raffinate stream which is removed from zone 1 can bepassed into zone 4 to displace desorbent material present in that zoneout of that zone into the desorption zone. Zone 4 will contain enoughadsorbent so that raffinate material present in the raffinate streampassing out of zone 1 and into zone 4 can be prevented from passing intozone 3, thereby contaminating extract stream removed from zone 3. In theinstances in which the fourth operational zone is not utilized, theraffinate stream passed from zone 1 to zone 4 must be carefullymonitored in order that the flow directly from zone 1 to zone 3 can bestopped when there is an appreciable quantity of raffinate materialpresent in the raffinate stream passing from zone 1 into zone 3 so thatthe extract outlet stream is not contaminated.

A cyclic advancement of the input and output streams through the fixedbed of adsorbent can be accomplished by utilizing a manifold system inwhich the valves in the manifold are operated in a sequential manner toeffect the shifting of the input and output streams, thereby allowing aflow of fluid with respect to solid adsorbent in a countercurrentmanner. Another mode of operation which can effect the countercurrentflow of solid adsorbent with respect to fluid involves the use of arotating disc valve in which the input and output streams are connectedto the valve and the lines through which feed input, extract output,desorbent input and raffinate output streams pass are advanced in thesame direction through the adsorbent bed. Both the manifold arrangementand disc valve are known in the art. Specifically, rotary disc valveswhich can be utilized in this operation can be found in U.S. Pat. No.3,040,777 and 3,422,848. Both of the aforementioned patents disclose arotary type connection valve in which the suitable advancement of thevarious input and output streams from fixed sources can be achievedwithout difficulty.

In many instances, one operational zone will contain a much largerquantity of adsorbent than some other operational zone. For instance, insome operations the buffer zone can contain a minor amount of adsorbentas compared to the adsorbent required for the adsorption andpurification zones. It can also be seen that in instances in whichdesorbent is used which can easily desorb extract material from theadsorbent, a relatively small amount of adsorbent will be needed in adesorption zone as compared to the adsorbent needed in the buffer zoneor adsorption zone or purification zone or all of them. Since it is notrequired that the adsorbent be located in a single column, the use ofmultiple chambers or a series of columns is within the scope of theinvention.

It is not necessary that all of the input or output streams besimultaneously used, and, in fact, in many instances some of the streamscan be shut off while others effect an input or output of material. Theapparatus which can be utilized to effect the process of this inventioncan also contain a series of individual beds connected by connectingconduits upon which are placed input or output taps to which the variousinput or output streams can be attached and alternately and periodicallyshifted to effect continuous operation. In some instances, theconnecting conduits can be connected to transfer taps which during thenormal operations do not function as a conduit through which materialpasses into or out of the process.

It is contemplated that at least a portion of the extract output streamwill pass into a separation means wherein at least a portion of thedesorbent material can be separated to produce an extract productcontaining a reduced concentration of desorbent material. Preferably,but not necessary to the operation of the process, at least a portion ofthe raffinate output stream will also be passed to a separation meanswherein at least a portion of the desorbent material can be separated toproduce a desorbent stream which can be reused in the process and araffinate product containing a reduced concentration of desorbentmaterial. The separation means will typically be a fractionation columnor an evaporator, the design and operation of either being well-known tothe separation art.

Reference can be made to D. B. Broughton, U.S. Pat. No. 2,985,589, andto a paper entitled "Continuous Adsorptive Processing--A New SeparationTechnique" by D. B. Broughton presented at the 34th Annual Meeting ofthe Society of Chemical Engineers at Tokyo, Japan, on Apr. 2, 1969, forfurther explanation of the simulated moving bed countercurrent processflow scheme.

A dynamic testing apparatus is employed to test various adsorbents witha particular feed mixture and desorbent material to measure theadsorbent characteristics of adsorptive capacity, selectivity andexchange rate. The apparatus consists of an adsorbent chamber ofapproximately 70 cc volume having inlet and outlet portions at oppositeends of the chamber. The chamber is contained within a temperaturecontrol means and, in addition, pressure control equipment is used tooperate the chamber at a constant predetermined pressure. Quantitativeand qualitative analytical equipment such as refractometers,polarimeters and chromatographs can be attached to the outlet line ofthe chamber and used to detect quantitatively to determine qualitativelyone or more components in the effluent stream leaving the adsorbentchamber. A pulse test, performed using this apparatus and the followinggeneral procedure, is used to determine selectivities and other data forvarious adsorbent systems. The adsorbent is filled to equilibrium with aparticular desorbent material through the adsorbent chamber. At aconvenient time, a pulse of feed containing known concentrations of atracer and of a particular ketose or aldose or both all diluted indesorbent is injected for a duration of several minutes. Desorbent flowis resumed, and the tracer and the ketose and aldose are eluted as in aliquid-solid chromatographic operation. The effluent can be analyzedon-stream or alternatively effluent samples can be collectedperiodically and later analyzed separately by analytical equipment andtraces of the envelopes of corresponding component peaks developed.

From information derived from the test adsorbent, performance can berated in terms of void volume, retention volume for an extract or araffinate component, selectivity for one component with respect to theother, the rate of desorption of an extract component by the desorbentand the extent of silica contamination of the extract and raffinatestream. The retention volume of an extract or a raffinate component maybe characterized by the distance between the center of the peak envelopeof an extract or a raffinate component and the peak envelope of thetracer component or some other known reference point. It is expressed interms of the volume in cubic centimeters of desorbent pumped during thistime interval represented by the distance between the peak envelope.Selectivity, (B), for an extract component with respect to a raffinatecomponent may be characterized by the ratio of the distance between thecenter of the extract component peak envelope and the tracer peakenvelope (or other reference point) to the corresponding distancebetween the center of the raffinate component peak envelope and thetracer peak envelope. The rate of exchange of an extract component withthe desorbent can generally be characterized by the width of the peakenvelopes at half intensity. The narrower the peak width the faster thedesorption rate.

To further evaluate promising adsorbent systems and to translate thistype of data into a practical separation process requires actual testingof the best system in a continuous countercurrent moving bed orsimulated moving bed liquid-solid contacting device. The generaloperating principles of such a device are as described hereinabove. Aspecific laboratory-size apparatus utilizing these principles isdescribed in deRosset et al U.S. Patent 3,706,812. The equipmentcomprises multiple adsorbent beds with a number of access lines attachedto distributors within the beds and terminating at a rotary distributingvalve. At a given valve position, feed and desorbent are beingintroduced through two of the lines and the raffinate and extractstreams are being withdrawn through two more. All remaining access linesare inactive and when the position of the distributing valve is advancedby one index all active positions will be advanced by one bed. Thissimulates a condition in which the adsorbent physically moves in adirection countercurrent to the liquid flow. Additional details on theabove-mentioned adsorbent testing apparatus and absorbent evaluationtechniques may be found in the paper "Separation of C₈ Aromatics byAdsorption" by A. J. deRosset, R. W. Neuzil, D. J. Korous, and D. H.Rosback presented at the American Chemical Society, Los Angeles, Calif.,Mar. 28 through Apr. 2, 1971.

Although both liquid and vapor phase operations can be used in manyadsorptive separation processes, liquid-phase operation is required forthis process because of the lower temperature requirements and becauseof the higher yields of extract product that can be obtained withliquid-phase operation over those obtained with vapor-phase operation.Adsorption conditions will include a temperature range of from about 20°C. to about 200° C. with about 20° C. to about 100° C. being morepreferred and a pressure range of from about atmospheric to about 500psig with from about atmospheric to about 250 psig being more preferredto insure liquid phase. Desorption conditions will include the samerange of temperatures and pressures as used for adsorption conditions.

The size of the units which can utilize the process of this inventioncan vary anywhere from those of pilot-plant scale (see for example ourassignee's U.S. Pat. No. 3,706,812) to those of commercial scale and canrange in flow rates from as little as a few cc an hour up to manythousands of gallons per hour.

The following examples are presented to illustrate our invention and arenot intended to unduly restrict the scope and spirit of the claimsattached hereto.

EXAMPLE I

The purpose of this example is to illustrate the method of manufactureof the adsorbent of this invention as well as three other adsorbentshaving organic polymer binders. Three different adsorbent samples wereprepared, each such preparation by the following steps:

(1) Na-Y type zeolite powder was mixed with the organic polymercomprising cellulose acetate powder for one of the samples, celluloseacetate butyrate for one of the samples and ethylcellulose for theadsorbent of this invention.

(2) An organic solvent was added to the powder mixture slowly and withmulling to obtain an extrudable mixture.

(3) The extrudable mixture was extruded into an extrudate.

(4) The extrudate was dried at 65° C.

(5) The dried extrudate was granulated and screened so as to obtainparticles sized from 30 to 60 mesh.

(6) The cations occupying exchangeable cationic sites in the zeolitecontained in the particles were ion exchanged with calcium ions bycontacting the particles with an aqueous solution of calcium chloride,washing the particles with fresh deionized water and air, and drying theparticles at room temperature.

EXAMPLE II

The purpose of this example is to present the results of long termstability tests of each of the adsorbents of Example I, except that twosuch tests were run for the cellulose acetate butyrate bound adsorbent.In this test 30 ml of each adsorbent was placed in a 250 ml containerwith 100 ml of distilled water. The samples were placed in an oven for15 days at 85° C. and the container for each adsorbent was swirled onceeach day. The following analysis of each decanted solution was thenobtained:

    ______________________________________                                                         Wt. PPM                                                                       Ca    Na     Al      Si                                      ______________________________________                                        Cellulose Acetate  41      59     ≦1.3                                                                         210                                   Cellulose Acetate Butyrate (1)                                                                   4.9     51     ≦1.3                                                                         161                                   Cellulose Acetate Butyrate (2)                                                                   5.9     53     ≦1.3                                                                         190                                   Ethylcellulose     1.7     11     ≦1.0                                                                         155                                   ______________________________________                                    

It can be seen from the above results that the adsorbent bound withethylcellulose, which is the adsorbent of this invention, has far lesstendency to dissolve than the other adsorbents.

EXAMPLE III

The adsorbent samples of Example I, along with a conventional clay boundzeolite adsorbent, were subjected to an attrition resistance test. Inthis test the sample is placed on a screen, having a certain mesh ornumber of openings per inch, with a certain number of uniform sizecoins. The screen is covered, placed in a sieve shaker or shaken for 30minutes. The increase in the amount of fines through the screen, basedon recovered sample, over the amount of sample that passes through thescreen in a subsequent test without coins, is calculated to be theweight percent attrition.

Following are the results of the attrition resistance tests:

    ______________________________________                                                                   Cellulose                                                   Conventional                                                                           Cellulose                                                                              Acetate  Ethyl-                                             Clay     Acetate  Butyrate cellulose                                          Bound    Bound    Bound    Bound                                     ______________________________________                                        Through 50 Mesh                                                                          6.2        3.2      1.5    2.4                                     Through 60 Mesh                                                                          4.8        2.2      0.8    2.0                                     ______________________________________                                    

The above results show attrition resistance of the adsorbent of thisinvention is second only to the cellulose acetate butyrate boundadsorbent.

EXAMPLE IV

The purpose of this example is to present the results of tests of eachof the adsorbents, prepared as set forth in the above Example I, in thedynamic testing apparatus hereinbefore described to determined theperformance of each such adsorbent with regard to the adsorptiveseparation of the individual components of an aqueous solution of amixture of components. Also tested for purposes of comparison with theabove adsorbents of our invention was a conventional 20% clay boundcalcium exchanged zeolite adsorbent.

The general pulse-test apparatus and procedure have been previouslydescribed. In this case, however, no on-stream GC analyzer was used tomonitor the effluent. Instead, the effluent was collected in anautomatic sample collector, and later each sample was injected into ahigh pressure liquid chromatograph (HPLC) for analysis. Each sample wascollected for a two minute period, and unlike the almost instantaneouscomponent concentration obtained with an on-stream GC, each samplerepresented an average of the component concentration over the twominute period of time.

The adsorbent test column consisted of a stainless steel tube 127 cmlong and 8.4 mm in internal diameter. This resulted in a test adsorbentbed of 70 cc. The feed consisted of 5 wt. % each of glucose, fructoseand sucrose and 20 vol. % of D₂ O (deuterium oxide) in deionized water.The desorbent was deionized water with a nominal pH value of 7.0.

The desorbent was run continously at a rate of 1 ml/min. Both feed anddesorbent were pumped under capillary flow control. At some convenienttime interval, the desorbent was stopped and the feed which was also runat a rate of 1 ml/min. was pumped for a period of 10 min. to deliver a10 ml "pulse". Immediately after the feed pulse was completed, thedesorbent flow was resumed and sample collection was begun. The twominute samples were collected for a period of 90 minutes, for a total of45 samples.

The effluent fractions were then sequentially injected into the HPLC foranalysis. From the analysis of these fractions, a chromatograph of theseparation of the feed components that were present in the feed pulsewere constructed. This was accomplished by plotting the peak height ofeach component versus the volume of effluent represented by the fractionfrom which the measurements were made. By joining the respective peakheights of each component, peak envelopes of the components wereobtained. The composite plot resembled a chromatogram of component peaksobtained from an analytical GC or LC of poor resolving power.

The sucrose, which is a disaccharide, evidently cannot enter the smallerselective pores of the adsorbent that the monosaccharides glucose andfructose can enter. Thus, the retention volume of the sucrose asmeasured, from the center of its peak envelope to the point where thefeed pulse was injected, was a measure of the void volume of the bed.The center of the sucrose peak envelope also served as the zero pointfor measuring the net retention volumes of the glucose, fructose and D₂O. The ratio of these net retention volumes was a measure of theselectivity (B) of the adsorbent for the more strongly adsorbedcomponent (larger net retention volume) with respect to the componentthat was less strongly adsorbed (smaller net retention volume).

The use of D₂ O (deuterium oxide) in this test allowed the measurementof the selectivity between the desorbent, water, and the more stronglyadsorbed component or extract, which was fructose. The ideal desorbentfor the Sorbex process is one that is adsorbed by the adsorbent justslightly less than the extract component, and more strongly than themost strongly adsorbed component that is rejected into the raffinate. Ingeneral, a selectivity of 1.1 to 1.4 for the extract component withrespect to the desorbent is ideal. The results for these pulse testswere as follows:

    ______________________________________                                                                  Cellulose                                                           Cellulose Acetate  Ethyl                                                Clay  Acetate   Butyrate cellulose                                            Bound Bound     Bound    Bound                                      ______________________________________                                        Half Widths                                                                   Fructose    14      13.79     13.75  13.47                                    Glucose     12      12.26     12.06  13.00                                    Sucrose     12.6    12.81     12.46  13.27                                    D.sub.2 O   10      11.08     9.71   9.12                                     Retention Volumes                                                             Fructose    13.2    10.41     11.11  10.81                                    Glucose     2.4     1.96      2.28   2.03                                     D.sub.2 O   12.8    12.22     13.49  13.34                                    F/G         5.5     5.32      4.86   5.33                                     F/D.sub.2 O 1.03    0.85      0.82   0.81                                     ______________________________________                                    

The above data illustrates that the performance of the adsorbent of thisinvention, with regard to adsorption of components from an aqueoussystem, compares quite favorably to other adsorbents, either inorganicor organic bound.

EXAMPLE V

The purpose of this example is to present the results of tests forsilica loss of adsorbents of this invention, conventional clay boundadsorbents and the other adsorbents prepared in Example I when contactedwith an aqueous stream. The testing apparatus comprised means forpumping, metering and maintaining a specific temperature of an aqueousstream; a first and second column each of 20 cc capacity in which theadsorbent to be tested was packed; and a first and second filter. Theflow of the aqueous stream was from the pumping, metering andtemperature control means through the first column, then through thefirst filter, then through the second column and finally through thesecond filter. Sample taps enabled sampling of the aqueous stream atpoints immediately downstream of each filter, the samples from the firsttap being referred to as "Col. 1 Raff.", and the samples from the secondtap being referred to as "Col. 2 Raff.". The purpose of having twopacked columns was to enable a determination of whether an equilibriumconcentration of silicon in the aqueous stream was reached in flowingthrough the first column, or whether such equilibrium was not reachedand the concentration of silicon would continue to increase during flowthrough the second column.

Four test runs using the above apparatus were made. For the first run,the columns were packed with the conventional clay bound adsorbentdescribed in Example IV, in the second run the column was packed withcellulose acetate bound Ca-Y zeolite, in the third run the column waspacked with cellulose acetate butyrate bound Ca-Y zeolite, while in thefourth run the column was packed with an adsorbent of our inventioncomprising a zeolite with an ethyl cellulose binder. Each test run wasover an extended period of time during which samples of the aqueousstreams were periodically taken from both of the sample taps andanalyzed for silicon concentration. The cumulative amount of effluentfrom the apparatus was measured at each time samples were taken andnoted as "Total Raff.". The following Tables 1, 2, 3 and 4 present thedata obtained from the first, second, third and fourth runs,respectively.

                  TABLE 1                                                         ______________________________________                                        CLAY BOUND FRESH ADSORBENT IN BOTH COLUMNS                                    H.sub.2 O pH = 8.5; Temp., 65° C.                                      Total Raff.                                                                            Col. #1 Raff.                                                                              Col. #2 Raff.                                           (Liter)  PPM Si    pH     PPM Si  pH   LHSV                                   ______________________________________                                        7.2      9.4       8.6    11.7    8.7  20.0                                   16.8     9.4       8.7    12.7    8.7  20.0                                   27.2     7.5       8.7    10.3    8.6  20.0                                   37.0     6.6       8.6    10.3    8.6  20.0                                   46.6     6.1       8.7    8.9     8.6  20.0                                   56.3     5.2       8.6    9.4     8.5  20.0                                   66.1     5.6       8.5    9.4     8.7  20.0                                   75.5     4.7       8.7    8.0     8.7  20.0                                   85.1     5.0       8.7    8.5     8.6  20.0                                   94.7     5.2       8.8    8.5     8.6  20.0                                   104.3    3.8       8.4    7.1     8.6  20.0                                   106.4    11.8      8.2    14.6    8.0  2.0                                    107.3    12.2      7.9    14.6    8.1  2.0                                    ______________________________________                                         Adsorbent Weight Loss from Col. #1 = 1.87 g.                                  Adsorbent Weight Loss from Col. #2 = 1.10 g.                             

                  TABLE 2                                                         ______________________________________                                        CELLULOSE ACETATE BOUND Ca-Y ZEOLITE                                          H.sub.2 O pH = 8.5; Temp., 65° C.                                      Total Raff.                                                                            Col. #1 Raff.                                                                              Col. #2 Raff.                                           (Liter)  PPM Si    pH     PPM Si  pH   LHSV                                   ______________________________________                                        7.3      7.0       8.1    12.0    8.6  20.0                                   16.9     7.5       8.8    8.9     8.6  20.0                                   26.5     3.8       8.6    5.6     8.6  20.0                                   36.1     2.4       8.5    4.2     8.4  20.0                                   45.7     2.8       7.9    4.2     8.5  20.0                                   55.3     2.8       8.5    4.0     8.6  20.0                                   65.0     2.6       7.6    3.5     8.7  20.0                                   74.1     2.6       8.5    4.2     8.7  20.0                                   78.0     10.3      7.5    13.2    8.4  2.0                                    79.0     9.4       8.5    13.2    8.5  2.0                                    80.2     8.5       7.8    12.2    8.3  2.0                                    86.6     3.1       7.5    4.0     8.6  20.0                                   96.4     2.4       7.4    3.1     8.4  20.0                                   105.9    2.4       7.9    3.3     8.3  20.0                                   115.4    2.4       7.1    3.1     7.1  20.0                                   ______________________________________                                         Adsorbent Weight Loss from Col. #1 = 0.82 g.                                  Adsorbent Weight Loss from Col. #2 = 0.44 g.                             

                  TABLE 3                                                         ______________________________________                                        Ca-Y ZEOLITE BOUND WITH CELLULOSE ACETATE                                     BUTYRATE                                                                      H.sub.2 O pH = 8.5; Temp., 65° C.                                      Total Raff.                                                                            Col. #1 Raff.                                                                              Col. #2 Raff.                                           (Liter)  PPM Si    pH     PPM Si  pH   LHSV                                   ______________________________________                                        2.4      --        --     13.9    8.4  20.0                                   7.8      7.5       8.6    11.3    8.5  20.0                                   16.8     4.7       8.8    7.5     8.7  20.0                                   26.4     3.5       8.9    5.6     8.9  20.0                                   36.0     3.3       8.8    4.5     8.8  20.0                                   45.6     2.4       8.7    3.5     8.8  20.0                                   55.1     2.6       8.9    3.8     8.9  20.0                                   64.6     2.6       8.9    3.7     8.9  20.0                                   79.2     2.8       8.9    4.0     8.8  20.0                                   88.4     10.8      --     13.2    --   2.0                                    89.4     8.9       --     12.7    --   2.0                                    91.4     8.5       --     11.3    --   2.0                                    92.3     9.4       --     11.8    --   2.0                                    95.3     --        --     --      --   20.0                                   100.2    2.6       --     3.3     --   20.0                                   ______________________________________                                         Adsorbent Weight Loss from Col. #1 = 0.82 g.                                  Adsorbent Weight Loss from Col. #2 = 0.46 g.                             

                  TABLE 4                                                         ______________________________________                                        20% ETHYLCELLULOSE AND 80% Ca-Y ADSORBENT                                     H.sub.2 O pH = 8.5; Temp., 65° C.                                      Total Raff.                                                                            Col. #1 Raff.                                                                              Col. #2 Raff.                                           (Liter)  PPM Si    pH     PPM Si  pH   LHSV                                   ______________________________________                                        7.2      4.7       --     10.3    --   20.0                                   16.9     5.2       8.54   7.5     8.62 20.0                                   26.5     3.3       8.15   5.2     8.23 20.0                                   36.0     2.6       8.00   4.2     8.09 20.0                                   45.7     2.4       7.94   2.8     7.60 20.0                                   55.3     2.6       8.85   2.8     8.70 20.0                                   64.9     2.4       8.78   2.8     8.80 20.0                                   74.5     3.1       8.5    3.5     8.8  20.0                                   84.2     3.1       8.85   3.8     9.0  20.0                                   89.6     8.5       8.1    9.4     8.6  2.0                                    90.6     8.0       --     10.6    --   2.0                                    91.5     8.0       8.4    10.3    8.6  2.0                                    99.5     2.1       8.5    2.6     8.6  20.0                                   109.2    2.8       8.5    3.5     8.6  20.0                                   ______________________________________                                         Adsorbent Weight Loss from Col. #1 = 0.65 g.                                  Adsorbent Weight Loss from Col. #2 = 0.00 g.                             

From a comparison of the data in the foregoing Tables, it is clearlyillustrated that the adsorbent of our invention (that bound withethylcellulose) has an amazing resistance to dissolution, far superiorto all of the other adsorbents tested. This resistance to dissolution isa surprising and unexpected improvement over that realized withadsorbents using known organic binders.

We claim as our invention:
 1. A process for the separation of acomponent from a feed mixture comprising an aqueous solution of amixture of components by contacting said solution with an adsorbentconsisting essentially of a crystalline aluminosilicate and a celluloseether binder to reduce the extent of disintegration of said adsorbent,wherein said adsorbent exhibits adsorption selectivity towards saidcomponent to separate said component from said feed mixture andthereafter recovering said selectively adsorbed component.
 2. Theprocess of claim 1 further characterized in that said cellulose ethercomprises ethyl cellulose.
 3. The process of claim 1 furthercharacterized in that said crystalline aluminosilicate is selected fromthe group consisting of X zeolites and Y zeolites.
 4. The process ofclaim 3 further characterized in that said aluminosilicate comprisesY-zeolite containing calcium cations at exchangeable cationic sites. 5.The process of claim 1 further characterized in that said feed mixturecomprises an aqueous solution of saccharides.
 6. The process of claim 5further characterized in that said saccharides comprise a mixture offructose and glucose.
 7. The process of claim 5 further characterized inthat recovery of said adsorbed component is effected with a desorbentcomprising water.
 8. The process of claim 5 further characterized inthat the pH of said aqueous solution is from about 5.0 to about 8.0. 9.The process of claim 1 further characterized in that the content of saidcellulose ether in said adsorbent is from about 3.0 wt. % to about 50.0wt. %.